LOCATION STIMSON WAEstablished Series
TAXONOMIC CLASS: Fine-silty, isotic, acid, mesic Typic Humaquepts
TYPICAL PEDON: Stimson silt loam, forested. (Colors are for moist soil unless otherwise noted.)
01--2 inches to 0; leaf litter partially decomposed; many very fine to very coarse roots; abrupt smooth boundary. (1 to 4 inches thick)
A11--0 to 6 inches; very dark brown (10YR 2/2) silt loam, grayish brown (10YR 5/2) dry; weak very fine and fine subangular blocky structure; soft, very friable, nonsticky and slightly plastic; common very fine to coarse roots; common very fine and fine tubular pores; medium acid (pH 5.8); clear wavy boundary. (4 to 7 inches thick)
A12--6 to 11 inches; very dark gray (10YR 3/1) silt loam, light brownish gray (10YR 6/2) dry; weak very fine, fine and medium subangular blocky structure; slightly hard, very friable, nonsticky and slightly plastic; common very fine, fine and medium roots; common very fine tubular pores; medium acid (pH 6.0); gradual wavy boundary. (3 to 6 inches thick)
B2g--11 to 19 inches; gray (10YR 5/1), brown (10YR 5/3) rubbed, silty clay loam, light gray (10YR 7/1), pale brown (10YR 6/3) rubbed, dry; common medium prominent reddish yellow (7.5YR 6/8) mottles, yellowish red (5YR 6/8) dry; massive; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; few very fine tubular pores; very strongly acid (pH 4.8); gradual wavy boundary. (6 to 12 inches thick)
Cg--19 to 60 inches; grayish brown (10YR 5/2), yellowish brown (10YR 5/4) rubbed, silty clay loam, light gray (10YR 7/1), yellow (10YR 7/6) rubbed, dry; common fine prominent red (2.5YR 4/6) mottles, reddish yellow (5YR 6/8) dry, and many large yellowish brown (10YR 5/8) mottles, reddish yellow (7.5YR 6/6) dry; massive; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; few very fine tubular pores; very strongly acid (pH 4.8).
TYPE LOCATION: Wahkiakum County, Washington; 50 feet north, 20 feet east of center of NW1/4 section 22, T.8N., R.5W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 49 to 52 degrees F. The soil ranges from medium acid in the surface to very strongly acid in the control section. The particle size control section is silty clay loam or silt loam, 20 to 35 percent clay and less than 15 percent particles coarser than very fine sand. The umbric epipedon is 7 to 9 inches thick.
The A horizon has value of 1, 2 or 3 moist, 5 or 6 dry, and chroma of 1 or 2 moist, 2 or 3 dry and is mottled in some pedons. Value of 6 dry is only in the lower part of the horizon. This horizon has weak very coarse to very fine subangular blocky structure.
The B horizon has value of 4 or 5 moist, 6 or 7 dry, and chroma of 1 (2 or 3 rubbed) moist or dry and is mottled. This horizon has weak angular blocky structure or is massive.
The C horizon has value of 5 or 6 moist, 6 or 7 dry, and chroma of 1 through 3 moist and 1 or 2 dry. The mottles have hue of 2.5YR through 10YR, value of 4 through 6 moist, 5 or 6 dry, and chroma of 6 through 8 moist or dry. It is silty clay loam or silt loam.
COMPETING SERIES: These are the closely related Bellingham and Nemah series. Bellingham soils are medium acid or slightly acid, have a mollic epipedon and have more than 35 percent clay in the control section. Nemah soils have more than 35 percent clay in the control section.
GEOGRAPHIC SETTING: Stimson soils are in depressions on uplands at elevations of 500 to 1,500 feet. These soils formed in fine textured loess. They are in coastal marine climate with relatively cool summers and mild, wet winters. They have an annual precipitation of 60 to 100 inches. The average January temperature is 38 degrees F.; the average July temperature is 64 degrees F.; and the mean annual temperature is 51 degrees F. The frost free season is 220 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Germany and Hoquiam soils. Germany and Haquiam soils are well drained and lack mottles.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; slow permeability.
USE AND VEGETATION: Used for timber production. The principal native vegetation is red alder, western red cedar, and an understory of ferns, salmonberry, and devil's club.
DISTRIBUTION AND EXTENT: Southwestern Washington. The soil is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Mason County, Washington, 1950.